XBMC is great, but it kinda randomly crashes a lot. There's nothing worse than turning on your TV and seeing that XBMC isn't running anymore. It's even worse when its your significant other or roomate and you're out of town. #tvops.
So just install this launchd
script to keep XBMC always running. This will launch it on boot, and if it crashes, it'll re-launch it.
mkdir ~/Library/LaunchAgents